1. Field of the Invention
The field of this invention relates to copolyimides, polyimides, polyimides-amides and copolyimides-amides prepared from tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride (TMCDA) dicarboxylic acids and a mixture of diamines. These novel polyimides-amides, copolyimides-amides are useful in preparing molded articles, fibers, films, laminates and coatings.
2. Background
It is known to make copolyimides from pyromellitic dianhydride and aromatic diamines. This is disclosed in U.S. Pat. No. 3,179,634 (1965). British Pat. No. 570,858 discloses various processes for making fiber forming polymers. The Japanese Patents listed below disclose the preparation of polyimides starting with cyclobutane-1,2,3,4-tetracarboxylic dianhydride.
Nos. JA 7123917-S27, JA 7137733-S44, JA 7137734-S44, JA 7219710-T23, and JA 72199098-T23. The article by F. Nakanishi and M. Hasegawa, Polymers, 14, 440 (1973) discloses the use of cyclobutane-1,2,3,4-tetracarboxylic dianhydride and 1,3,-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride in the preparation of polyimides: In reviewing all these references, it is clear that the use of TMCDA to form polyimides, copolyimides, polyimides-amides and copolyimides-amides, useful as moldings, films, fibers, laminates, and coatings has not been contemplated in the prior art.
The general object of this invention is to provide novel polyimides-amides and copolyimides-amides based on TMCDA dicarboxylic acids and a mixture of diamine moieties. A more specific object of this invention is to provide polyimides, copolyimides from TMCDA moieties and mixtures of aliphatic, cycloaliphatic, araliphatic and aromatic moieties. Another object is to provide a process for the manufacture of polyimidesamides, from TMCDA, dicarboxylic acids and a mixture of diamines.
We have found that novel polyimides-amides can be formed by reacting TMCDA with a mixture of diamines and diacids. TMCDA reacts readily with the diacids and the diamine mixture to form high molecular weight polyimide-amides or copolyimide-amides. In the novel process both aliphatic and aromatic diamines can be copolymerized with TMCDA and dicarboxylic acid in the melt to form high molecular weight polyamide-imides.
Our process for the manufacture of the novel polyimides-amides comprises reacting about equal molar amounts of the total TMCDA and dicarboxylic acid with a primary diamine or a mixture of primary diamines. The molecular ratio of TMCDA and dicarboxylic acid to the mixture of primary diamines may be in the range of about 1.3:1.0 to about 1.0:1.3 preferably, in the range of about 1.00 to 1.00. The molecular ratio of TMCDA to the dicarboxylic acid can be in the range of about 1:10 to about 10:1. Suitably, the reaction is conducted as a batch reaction at a temperature of about 130.degree. to 300.degree. C. for a period of about 0.25 to 6.0 hours in a nitrogen-containing organic polar solvent such as 1-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide or pyridine. The polycondensation can also be carried out as a continuous process. The polycondensation can suitably be carried out at a temperature of about 0.degree. C. to about 200.degree. C., preferably at a temperature of about 50.degree. to about 100.degree. C. The novel copolyimides-copolyamides of this invention have the following recurring structure: ##STR1## wherein R, R' and R" are divalent aliphatic or aromatic hydrocarbon radicals. The radicals R, R' and R" are the same or different and may be divalent aliphatic hydrocarbons of 2 to 18 carbon atoms or an aromatic hydrocarbon from 6 to 20 carbon atoms, or an aromatic hydrocarbon radical containing from 6 to 10 carbon atoms joined directly or by stable linkage comprising --O--, methylene, ##STR2## --SO--, --SO.sub.2 --, and --S-- radicals. It should be noted that n and/or m integers from about 1 to about 10 and the ratio of n:m is about 10:1 to about 1:10. The radicals R and R' are derived from aliphatic, araliphatic or cycloaliphatic diamines such as ethylenediamine, propylenediamine, 2,2-dimethylpropylene diamine, tetramethylene diamine, hexamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, dodecamethylene diamine, 4,4'-diaminodicyclohexylethane, xylylene diamine and bis(aminomethyl)cyclohexane. Suitable aromatic diamines useful in our process include para- and -meta-phenylenediamine, 4,4'-oxydianiline, thiobis (aniline), sulfonylbis (aniline), diaminobenzophenone, methylenebis (aniline), benzidine, 1,5-diaminonaphthalene, oxybis (2-methylaniline), thiobis (2-methylaniline), and the like. Examples of other useful aromatic primary diamines are set out in U.S. Pat. No. 3,494,890 (1970) and U.S. Pat. No. 4,016,140 (1972) both incorporated herein by reference. The preferred diamine mixtures are 1,6-hexamethylenediamine and 1,12-dodecanediamine, 1,6-hexamethylenediamine and 4,4'-oxydianiline, 1,12-dodecanediamine and 4,4'-oxydianiline and 1,6-hexamethylenediamine and ethylene diamine. The ratio of the two diamines may be in the range of 19:1 to 1:19 preferably 3:1 to 1:3.
R" is derived from suitable dicarboxylic acids comprising the following structure: ##STR3## where X is OH, Cl, or O alkyl wherein the alkyl group comprises about 1 to about 5 carbon atoms and R" is a divalent aromatic or aliphatic radical. Advantageously R" is a divalent aliphatic hydrocarbon containing about 2-18 carbon atoms or an aromatic divalent radical containing about 1-3 benzene rings, or heterocyclic hydrocarbon or a mixture of these. The R" moiety is derived from aromatic diacids or their halides or esters such as oxalic acid, glutaric acid, adipic acid, azelaic acid, terephthalic acid, isophthalic acid, biphenyl-4,4'-dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, and pyridine-2,4- and 3,5-dicarboxylic acid.
In some cases the polyimide-amides or the copolyimides may be further polymerized under "solid state polymerization" conditions. The term solid state polymerization refers to chain extensions of polymer particles under conditions where the polymer particles retain their solid form and do not become a fluid mass. The solid state polymerization can be carried out below the melting point of the polymer or copolymer and can be conducted in several ways. However, all techniques require heating the ground or pelletized polymer below the melting point of the polymer, generally at a temperature of about 200.degree. to 300.degree. C. while either sparging with an inert gas, such as nitrogen or operating under vacuum. In cases where the polymer has a low melt temperature, it can be polymerized in the melt under vacuum in thin sections or using thin film reactors known in the art.
Injection molding of the novel polyimides, copolyimides, polyimide-amides and copolyimide-amide is accompanied by injecting the polymer into a mold maintained at a temperature of about 23.degree. to 200.degree. C. In this process a 20 second to 1 minute cycle is used with a barrel temperature of about 200.degree. C. to 350.degree. C. The latter will vary depending on the T.sub.g and T.sub.m of the polymer being molded.
The novel polyimides, copolyimides, polyimide-amides and copolyimide-amides have excellent mechanical and thermal properties and can readily be molded into useful articles or formed into fibers, films, laminates or coatings.
Analysis of the TMCDA-based polyimides and polyimide-amides by thermal gravimetric analysis shows excellent stability. This is demonstrated by the fact that under nitrogen atmosphere the 1 percent weight loss occurs at a temperature of 310.degree. C. and main weight loss occurs at a temperature of about 390.degree. C. Glass transition temperature T.sub.g of the polyimide varied with the particular diamine used as shown in the Examples.
Diamines with the amino groups attached directly to the aromatic ring are suitably copolymerized with TMCDA and diacids by solution condensation in organic polar solvents. Useful polar solvents include N,N-dimethylacetamide, 1-methyl-2-pyrrolidinone, N,N-dimethylformamide, dimethylsulfoxide and the like.
The polymers and copolymers were cast into films. The films were heated at a temperature of about 200.degree. C. for 10 minutes. The dry film was 10 mm in thickness and was transparent.
We have found that the polymers and copolymers of this invention are improved by the addition of reinforcing material particularly, the mechanical properties of the polymers and copolymers are improved if these polymers and copolymers contain from about 25 to about 60 percent by weight glass fibers, glass beads, industrial minerals, such as talc or graphite or mixtures thereof. In the preferred range the polymers and copolymers contain about 30 to about 40 percent by weight of the glass fibers, glass beads, industrial minerals or graphite or mixtures thereof. Suitably reinforcing materials can be glass fibers, glass beads, glass spheres, glass fabrics. The glass fibers are made of alkali-free boron-silicate glass or alkali-containing C-glass. The thickness of the fiber is suitably on the average between 3 and 30 mm. It is possible to use both long fibers with average lengths of from 5 to 50 mm and also short fibers with an average filament length from 0.05 to 5 mm. In principle, any standard commercial-grade fibers, especially glass fibers, may be used. Glass beads ranging from 5 to 50 mm in diameter may also be used as a reinforcing material.
The reinforced polymers and copolymers may be prepared in various ways. For example, so-called rovings endless glass fiber strands are coated with the polyamic acid melt and subsequently granulated. The cut fibers or the glass beads may also be mixed with granulated polyamic acid and the resulting mixture melted in a conventional extruder, or alternatively the fibers may be directly introduced into the polyamic acid melt through a suitable inlet in the extruder. Injection molding of the novel glass-filled polymers and copolymers is accomplished by injecting the polyimide into a mold maintained at a temperature of about 23.degree. to 200.degree. C. In this process a 25 to 28 second cycle is used with a barrel temperature of about 200.degree. to 350.degree. C. The injection molding conditions are given in Table 1.
TABLE I ______________________________________ Mold Temperature 23.degree. to 200.degree. C. Injection Pressure 15,000 to 19,000 psi and held for 1 to 3 seconds Back Pressure 100 to 220 psi Cycle Time 25 to 28 seconds Extruder: Nozzle Temperature 200.degree. to 350.degree. C. Barrels: Front heated to 200.degree. to 350.degree. C. Screw: 20 to 25 revo- lutions/minute ______________________________________